For a better comparison, would it be possible to have also an option to convert the Links to only Part containers when exporting the file?

For exporting, there is no need to change object type, just call Part::getTopoShape(), which is the work horse behind python Part.getShape(). But then that means I'll have to change upstream exporter code. But what exactly do you want to compare by doing this?

Try Assembly3 (latest version 0.10.2) along with my custom build of FreeCAD at here.
And if you'd like to show your support, you can donate through patreon, liberapay, or paypal

For exporting, there is no need to change object type, just call Part::getTopoShape(), which is the work horse behind python Part.getShape(). But then that means I'll have to change upstream exporter code. But what exactly do you want to compare by doing this?

I would like to let both exporters cohabit till the new branch get a full stability with a larger user audience.

Just started testing, but it seems many issue have gone
I noticed that in some case, some of the STEP objects get strange colors... (here a test with arietta imported with both modes)

arietta-color-comparison.png (225.85 KiB) Viewed 719 times

I think this A3 branch would add a new 'STEP' improvement for CAD interoperability, apart the other big one on the assembly and constraints wb that was still missing

EDIT
frame rate is still better in FC mainstream with VBO enabled...
a part the fps displayed, you can see that the FC mainstream board is turning faster than the A3 branch one...
I'm using the following code for spinning comparison

I noticed that in some case, some of the STEP objects get strange colors... (here a test with arietta imported with both modes)

STEP file can save colors for both edge and face. And this particular STEP file sets both face and edge color with the same value. It is weird when displayed in FC. I'll ignore the edge color in case the shape has face, and the face color is the same as edge color.

I have trace the code for VBO rendering, at least on Linux, my code has no effect on VBO. That is really a mystery, and I really want to know why it behave like that on your machine. Here is a screencast showing the effect of VBO active and inactive. Rendering transparency disables VBO. The 17fps is about the same for App::Part on my machine.

Try Assembly3 (latest version 0.10.2) along with my custom build of FreeCAD at here.
And if you'd like to show your support, you can donate through patreon, liberapay, or paypal

I have trace the code for VBO rendering, at least on Linux, my code has no effect on VBO. That is really a mystery, and I really want to know why it behave like that on your machine. Here is a screencast showing the effect of VBO active and inactive. Rendering transparency disables VBO. The 17fps is about the same for App::Part on my machine.

I see your result ... this is strange...
I'm going to see if I can find the e-mails I had with Jean Marie about our VBO testing to get some tips...

BTW I made some test also on STEP with external references and the results are very good... an other very big STEP ahead!
Thx